Fluid pump with air inducer

Abstract

A screw-type fluid pump is provided with an elongate casing having a surface defining an internal fluid flow space and a screw within the flow path, fixed to the casing, and having a plurality of flights for continuously conveying fluid from an inlet on the casing to an outlet for appropriate disposition as the screw and casing are rotated. A conduit/torque tube extends through the screw in axially overlapping relationship with the casing over no more than one third the axial extent of the screw at the upper region of the casing. The conduit/torque tube establishes communication between a plurality of pockets between screw turns and the atmosphere to effect pressure equalization so that cavitation in the fluid flow space is prevented as the screw is operated. The conduit/torque tube also transmits the force from a rotary drive to the screw.

I claim: 
     
       1. A screw-type fluid pump comprising: an elongate casing having a surface defining an internal fluid flow space, a fluid inlet and a fluid outlet above the fluid inlet;   a fluid advancing screw having a rotational axis, a plurality of flights, and a central hollow core extending through the flights, and a central hollow core extending through the flights between the fluid inlet and the fluid outlet;   means mounting the screw fixedly to the casing in the fluid flow space so that the screw and casing can be rotated as a unit about an axis to convey fluid introduced at the inlet over the flights axially towards the outlet,   there being a plurality of axially spaced pockets between adjacent screw flights within the fluid flow space;   a conduit having a length no more than one third the axial extent of the screw;   means for mounting the conduit within the hollow core to the screw; and   means for connecting the conduit to a rotary drive so that the conduit, fluid advancing screw and casing can be rotated to raise a fluid from the casing inlet to the casing outlet,   said conduit having a wall bounding a hollow space, a first surface in direct radial exposure to the atmosphere and a second surface exposed to one of the pockets,   there further being first and second discrete apertures through the conduit wall with one of the first and second apertures extending through the first surface of the conduit and defining a communication path between the atmosphere and the hollow space and the other of the first and second apertures extending through the second surface of the conduit and defining a communication path between the hollow space and the one of the pockets,   whereby the conduit serves the dual purpose of transmitting a rotary drive force to the advancing screw and vents the one of the pockets to the atmosphere to prevent the development of vacuum therein.   
     
     
       2. The fluid pump according to claim 1 wherein there is a third aperture extending through the conduit, said second and third apertures communicate between the vent path and a first and second of the plurality of pockets, the first, second and third apertures extend radially through the conduit wall and there are fourth, fifth and sixth apertures extending radially through the conduit wall consecutively in substantially axial alignment with and circumferentially spaced from the first, second and third apertures. 
     
     
       3. The fluid pump according to claim 1 wherein the casing surface is substantially cylindrical and the conduit is coaxial with the casing surface. 
     
     
       4. The fluid pump according to claim 1 wherein said screw has axially spaced inlet and outlet ends and the conduit is in axially overlapping relationship over approximately one third of the axial extent of the screw at the outlet end thereof. 
     
     
       5. A screw-type fluid pump comprising: a casing having a cylindrical surface defining an internal fluid flow space with axially spaced inlet and outlet ends;   a fluid advancing screw having an inlet end, an outlet end and a plurality of flights defining a central hollow core extending axially the entire length of the screw;   means mounting the screw fixedly to the casing in the fluid flow space so that the screw and casing can be rotated as a unit about the axis of the casing surface to convey fluid at the inlet along the axis of the casing surface on the screw flights between the casing inlet and outlet,   there being a plurality of pockets defined between axially adjacent flights;   a conduit;   means for mounting the conduit to the fluid advancing screw at least partially within said fluid flow path, said conduit having a surface defining a vent path in communication with the hollow core, said surface of the conduit and vent path defined thereby extending axially above the outlet end of the casing with the surface of the conduit being exposed to the atmosphere;   first means communicating between the vent path and at least one of the pockets;   means for connecting the conduit to a rotary drive so that a drive force from the rotary drive is imparted to the screw and in turn the casing through the conduit; and   second means separate from said first means for communicating radially between the vent path and the atmosphere through a portion of the exposed surface of the conduit extending axially beyond the outlet end of the casing,   whereby the conduit serves the dual purpose of transmitting a rotary drive force to the advancing screw and vents the one of the pockets to the atmosphere to prevent the development of vacuum therein.   
     
     
       6. The screw-type fluid pump of claim 5 wherein bearing means surround the casing to mount the casing for rotation relative to a fixed pump support.